Many imaging apparatus, such as ink jet and electrophotographic printers, copiers and the like, utilize one or more media trays to hold a stack of sheets of media. A mechanism in the tray or in the printer housing separates and delivers individual sheets to the imaging apparatus for printing or copying. One well-known type of media tray takes the form of a rectangular bin having vertical walls for containing the stack of media. This type of tray utilizes springs and pressure plates to urge the stack of media upwardly against one or more drive rollers that feed individual sheets to the imaging apparatus.
Another type of tray and sheet delivery mechanism that does not use springs or pressure plates is disclosed in U.S. Pat. No. 5,377,969 (the '969 patent). FIG. 2 of the present application schematically illustrates a portion of this type of mechanism and tray, generally indicated by the reference numeral 30. The tray includes a bottom support surface 26 on which a stack of paper 14 is placed flat. At a delivery end of the support surface 26 is an inclined wall 32 that is oriented up and away from the support surface 26 and the stack of paper 14. The sheet delivery mechanism utilizes a sheet separator 11 that includes a support arm 12 and a roller 16 rotatably coupled to the arm. The separating roller 16 rests on the stack of media 14 and acts by friction to push individual sheets laterally against and upwardly along a slanted guide surface or ramp 6 on the upwardly inclined wall 32.
The support arm 12 is pivotally mounted in the printer housing to allow the arm to rise and fall with the height of the media stack 14 (indicated by action arrow A). The support arm 12 may also move laterally away from the ramp 6 and over the stack of media 14 (indicated by action arrow B). This lateral movement allows for a sufficient distance between the ramp 6 and the roller 16 to insure that the top sheet 4 bends between its front edge against the ramp and its contact line with the roller. This bending is necessary for the front edge of the sheet 4 to be pushed along the ramp 6 and lifted up from the stack 14. When the tray 30 is removed from the printer, the support arm 12 pivots upwardly and is stored behind the transport rollers 15, 17.
In proper operation, the separating roller 16 urges a sheet 4 upwardly along the ramp 6 and into a guide surface 10 that directs the sheet into the transport nip 8 for delivery to the printer. As illustrated in FIG. 2, however, in certain situations the sheet 4 can float or curl away from the ramp 6 and thereby miss the guide surface 10 and transport nip 8. This misfeed requires the user to remove the tray and clear the misfed sheet.
What is needed is a media guiding apparatus that reliably delivers a media sheet to the transport nip 8, while also allowing the support arm 12 to move freely within the tray during operation and to pivot upwardly for storage when the tray is removed.